Retinaldehyde is a mild retinoid that has been linked to increased epidermal thickness. It has been shown to improve skin radiance, wrinkles and fine lines. it has shown benefits for skin with acne, actinic keratosis and rosacea.

See also:

Retinoids
Retinoic Acid
Retinol
Retinyl Palmitate
Retinyl Ascorbate
Retinyl Retinoate


Ref:
Fluhr JW, Vienne MP, Lauze C, Dupuy P, Gehring W, Gloor M. Tolerance profile of retinol, retinaldehyde and retinoic acid under maximized and long-term clinical conditions. Dermatology. 1999;199 Suppl 1:57-60. doi: 10.1159/000051381. PMID: 10473963.

Fluhr JW, Vienne MP, Lauze C, Dupuy P, Gehring W, Gloor M. Tolerance profile of retinol, retinaldehyde and retinoic acid under maximized and long-term clinical conditions. Dermatology. 1999;199 Suppl 1:57-60. doi: 10.1159/000051381. PMID: 10473963.

Creidi P, Vienne MP, Ochonisky S, Lauze C, Turlier V, Lagarde JM, Dupuy P. Profilometric evaluation of photodamage after topical retinaldehyde and retinoic acid treatment. J Am Acad Dermatol. 1998 Dec;39(6):960-5. doi: 10.1016/s0190-9622(98)70270-1. PMID: 9843009.